A Practical Review of Functional MRI Anatomy of the Language and Motor Systems

Abstract

Functional MR imaging is being performed with increasing frequency in the typical neuroradiology practice; however, many readers of these studies have only a limited knowledge of the functional anatomy of the brain. This text will delineate the locations, anatomic boundaries, and functions of the cortical regions of the brain most commonly encountered in clinical practice-specifically, the regions involved in movement and language.

Fig 1.

Sagittal 3D-FLAIR image with a superimposed diffusion tensor image of the arcuate fasciculus between the inferior parietal lobule (pars opercularis and pars triangularis) (green) and the angular gyrus (red). The frontotemporal segment of the arcuate fasciculus connects the Broca area at the inferior frontal gyrus with the Wernicke area more posteriorly, traditionally at the posterior superior temporal gyrus. However, this connection is variable, and in this case, it is at the angular gyrus/posterior superior temporal area.

Fig 2.

A, Axial MPRAGE image through the sensorimotor cortex with functional areas labeled in the right cerebral hemisphere. B, Coronal contrast-enhanced MPRAGE image with superimposed diffusion tensor imaging view of the corticospinal tract. DLPC, dorsolateral prefrontal cortex; SMA, supplementary motor area.

Fig 3.

DWI (A) and ADC map (B) demonstrate a left hand/arm motor infarct in a patient with sudden onset of right-arm weakness. C, DWI demonstrates a left facial motor infarct in a patient with facial weakness.

Fig 4.

Functional MR imaging blood oxygen level–dependent activation of the SMA superimposed on axial (A) and sagittal (B) MPRAGE images. Dark blue designates activation during antonym generation; turquoise, during picture naming; purple, during rhyming; light blue, during silent word generation; yellow, during finger movement; and green, during lip movement.

Fig 5.

A patient with a left precentral gyrus/paracentral lobule and an SMA mass who initially presented with seizure. A, Axial T2-weighted MR imaging shows a left SMA mass. The patient underwent subtotal resection complicated by transient postoperative right hemiparesis (SMA syndrome). Pathology showed a diffuse infiltrating astrocytoma, isocitrate dehydrogenase-mutant, World Health Organization grade II. DTI superimposed on coronal FLAIR (B) and axial functional MR imaging show right foot (C) and language (D) SMA activation at the margins of the mass.

Fig 6.

A, Sagittal MPRAGE image through the inferior parietal lobule demonstrates the supramarginal gyrus and angular gyrus. The superior temporal gyrus also is highlighted. Axial DWI (B) and sagittal T1-weighted (C) images of a left IPL infarct. The patient presented with the inability to understand and could not produce any comprehensible speech. The IPL is involved in semantic and phonologic processing. Patients with an infarct in this region have severe word- and sentence-comprehension deficits due to a transcortical sensory aphasia. Subdivisions of the arcuate fasciculus connect the IPL to the posterior temporal area as well as the IPL to the Broca area.

Fig 7.

A left Broca infarct with classic expressive aphasia. A, Axial diffusion-weighted image demonstrates restricted diffusion at the classic Broca area. B, Sagittal T1-weighted image demonstrates hypointensity due to edema from the infarct.